1. Field of the Invention
The present invention relates to an inkjet printer. In particular, the invention relates to temperature control of ink in a recording head.
2. Description of Related Art
As a recording terminal connected to a word processor, a personal computer or the like, various kinds of printers such as a dot impact printer, an inkjet printer, a laser printer, a thermal transfer printer, a dye sublimation printer or the like have been developed. Among all, compared with the printers of other systems, the inkjet printer has advantages that it is more noiseless during the recording and can record colorful images easier and more inexpensively. Therefore, the inkjet printer has been the mainstream of the printers.
In the inkjet printer, a recording head comprising many orifices (nozzles) is mounted in a carriage movable in the back-and-forth direction. The inkjet printer moves the carriage in the back-and-forth direction perpendicular to the conveyance direction of the recording medium. During the back-and-forth movement, the inkjet printer records an image by jetting the ink from each nozzle of the recording head onto the recording medium in accordance with image information. Here, viscosity of the ink jetted from each nozzle is changed according to the changes in temperature (viscosity increases according to decrease in temperature). For this reason, during the image-recording, the recording head is heated and controlled by a heater, and then the ink is jetted from each nozzle at a predefined temperature (a set value) set beforehand (for example, refer to Published Unexamined Japanese Patent Application No. S62-39261).
However, as for related inkjet printers, during the movement of the carriage, air flow occurs in the neighborhood of the nozzles of the recording head, and a temperature in the neighborhood of the nozzles becomes lower than that of outside air. For this reason, in practice, the ink jetted from each nozzle of the recording heads is jetted at lower temperature than the set value. Therefore, even if the optimal set value for the image-recording has been set, the viscosity of the ink increases according to decrease of its temperature. As a result, the ink having an optimal viscosity for the image-recording is not always jetted from each nozzle during the image-recording.